Background: Individuals with DMD experience high rates of bone fragility, fractures, and osteoporosis, which can affect both quality and quantity of life. Preventing fractures is an important therapeutic goal, but research into fracture prevention is challenging due to a lack of biomarkers that robustly predict fracture risk. Magnetic resonance imaging can be used to measure bone dimensions, which may capture meaningful changes with disease progression and therapeutic intervention.
Objectives: To evaluate changes in mid-femur cortical thickness relative to body size in corticosteroid treated and untreated individuals with DMD and unaffected controls.
Approach: This analysis uses data from the ImagingDMD study, a longitudinal multicenter study of muscle MR in DMD. The ImagingDMD study has 175 affected participants, who have visited one of 3 study sites annually for 1-9 years. In this sub-analysis, we have measured the femur on 3 contiguous axial T1-weighted MRI slices in 55 affected and 44 unaffected individuals. The endosteal and periosteal borders were manually segmented and used to calculate mean cortical thickness. Cortical thickness was normalized to body surface area.
Results: Boys with DMD had significantly lower cortical thickness than age matched controls (0.32 ± 0.06 vs 0.39 ± 0.06 cm/m2). In young (5-10 year old) boys with DMD, cortical thickness was significantly lower in corticosteroid treated vs corticosteroid naïve individuals (0.32 ± 0.05 vs 0.39 ± 0.05, p=0.02). Vastus lateralis fat fraction, an MRI measure of muscle health, was significantly correlated with cortical thickness (R2=0.31, p<0.0001). In a small number of nonambulatory participants, cortical thickness was lower than ambulatory individuals (0.27 ± 0.04 vs 0.32 ± 0.06).
Conclusions: Cortical thickness captures bone deficits in individuals with DMD, and may be a promising noninvasive measure to include in studies of bone health in individuals with muscular dystrophy.